2. Experiments of this kindin both the U.S. and Europe well before the Second World War.
A.have conducted
B.have been conducted
C.had conducted
D.had been conducted
【解析】句意为：第二次世界大战之前，在美国和欧洲就曾彻底地进行过这种实验。本题考查时态和语态。experiments与conduct之间为被动关系，故排除A项和C项。conduct这一动作发生在第二次世界大战之前，即：过去的过去，所以用过去完成时，故选择D项。
【答案】D
